JP6360505B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine.

  Conventionally, an overhanging part that protrudes toward the intake valve side is formed on the inner peripheral surface of the intake port of the internal combustion engine, and the overhanging part controls the direction of intake air flowing through the intake port to generate a strong swirl in the combustion chamber The technique to make is known (for example, refer patent document 1).

JP 2000-64843 A

In Patent Document 1, the projecting portion in the intake port projects inward from the inner diameter of the valve seat, so that the cross-sectional area of the passage is reduced, pressure loss is increased, and improvement in combustion efficiency is suppressed.
An object of the present invention is to provide an internal combustion engine capable of improving the combustion efficiency by controlling the direction of the gas flow flowing into the combustion chamber without changing the passage sectional area.

In order to solve the above-described problems, the present invention provides a cylinder head (14) with a combustion chamber (30) and intake / exhaust ports (21a, 21b) communicating with the combustion chamber (30). , 21b) are opened and closed by intake and exhaust valves (63, 73) to the combustion chamber (30), and the intake port (21a) is tumbled into the combustion chamber (30). A partition plate (21h) for generating the intake air, and the partition plate (21h) divides the intake air flowing through the intake port (21a) into upper and lower intake passages (35, 36), In an internal combustion engine in which the exhaust valve (73) is opened and internal EGR is performed while the intake valve (63) is open, the exhaust port (21b) is opened on the combustion chamber (30) side. 54j) is provided with a valve seat (54) that contacts the umbrella portion (73b) of the exhaust valve (73) and closes the exhaust port (21b), and has a cylindrical end formed on the valve seat (54). inner peripheral surface and (54d), the clearance between the outer edge (73f) of the umbrella portion of the exhaust valve (73) (73b) (CL ), varies in the circumferential direction of the valve head (73b), the intake valve When the clearance (CL) closer to (63) is the near clearance (CN) and the clearance (CL) far from the intake valve (63) is the far clearance (CF), the near clearance (CN) ) than said distal clearance (CF) is characterized that you have been large.

In the above structure, before Symbol clearance (CL) it may also be gradually decreases as the exhaust valve (73) from the side toward the intake valve (63) side.

In the above structure, wherein the valve head of the exhaust valve (73) open while the front Symbol intake valve (63) is open sealing surface (73b) and (73c), said valve seat (54) seal When the maximum clearance with the surface (54c) is EGR clearance (CE), the EGR clearance (CE) is larger than the near clearance (CN), and the far clearance (CF) is larger than the EGR clearance (CE). May be large.

In the above structure, before Symbol clearance (CL), said end axis of the inner peripheral surface (54d) to (54f), the intake and exhaust valves (63 relative to the axis (73e) of said exhaust valve (73), 73) may be made to differ in the circumferential direction of the umbrella part (73b) by offsetting in the direction in which they are arranged.

In the present invention, the clearance between the inner peripheral surface of the end portion formed in the opening on the combustion chamber side of the exhaust port and the outer peripheral edge of the umbrella portion of the exhaust valve is different in the circumferential direction of the umbrella portion. During internal EGR by the exhaust valve, it is possible to form a flow of exhaust gas that flows into the combustion chamber in a direction that promotes tumble of the intake air, thereby improving combustion efficiency.
Also, when the clearance near the intake valve is the near clearance and the clearance (CL) far from the intake valve is the far clearance, the far clearance is larger than the near clearance. By changing the clearance between the inner peripheral surface of the end of the opening and the outer peripheral edge of the umbrella portion of the exhaust valve between the side close to the intake valve and the side far from the intake valve, the tumble of the intake is promoted during internal EGR by the exhaust valve A flow of exhaust gas flowing into the combustion chamber can be formed, and combustion efficiency can be improved.

  Further, since the clearance gradually decreases from the exhaust valve side toward the intake valve side, the area between the inner peripheral surface of the end of the opening on the combustion chamber side and the outer peripheral edge of the umbrella portion of the exhaust valve is far from the intake valve. Therefore, the exhaust gas can be effectively taken into the combustion chamber so as to promote tumble, and the combustion efficiency can be further improved.

  In addition, a valve seat that closes the exhaust port against the umbrella part of the exhaust valve is provided at the opening on the combustion chamber side of the exhaust port, and the sealing surface of the umbrella part of the exhaust valve that is opened while the intake valve is open, When the maximum clearance with the seal surface of the valve seat is the EGR clearance, the EGR clearance is larger than the near clearance and the far clearance is larger than the EGR clearance. By increasing the far clearance above the EGR clearance, a predetermined clearance is obtained. By opening the exhaust valve so as to achieve the EGR clearance, the exhaust can be made to flow along the tumble flow from the exhaust port into the combustion chamber through the gap that becomes the far clearance, thereby assisting the formation of the tumble flow. Further, by making the neighborhood clearance smaller than the EGR clearance, it is possible to make it difficult for exhaust to flow into the intake valve side of the combustion chamber so as not to disturb the tumble flow.

  The inner peripheral surface of the end is formed in the valve seat, and the clearance is offset in the circumferential direction of the umbrella by offsetting the axis of the inner peripheral surface of the end in the direction in which the intake and exhaust valves are aligned with the axis of the exhaust valve. Since it is made different, the clearance can be easily varied in the circumferential direction of the umbrella by simply processing the inner peripheral surface of the end of the valve seat, thereby reducing the cost and improving the productivity. Can do.

It is sectional drawing which shows the internal combustion engine of one Embodiment of this invention. It is sectional drawing which shows the state which the intake valve and the exhaust valve closed. It is sectional drawing which shows the effect | action of an intake valve and an exhaust valve. It is a principal part enlarged view of FIG. FIG. 4 is a view taken in the direction of arrow V in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an internal combustion engine 10 according to an embodiment of the present invention.
The internal combustion engine 10 includes a cylinder block 12 into which a piston 11 is movably inserted, a cylinder head 14 attached to the cylinder block 12 via a head gasket 13, and a head cover 16 that closes an upper opening of the cylinder head 14. .

The cylinder block 12 is provided with a plurality of fins 12a on the outer surface and a cylinder hole 12b on the inner side. Heat release from the cylinder block 12 is promoted by the plurality of fins 12a. The piston 11 is fitted in the cylinder hole 12b.
The cylinder head 14 includes a cylinder head body 21 made of aluminum alloy die casting, and a valve mechanism 22 attached to the cylinder head body 21.
The cylinder head body 21 includes an intake port 21a and an exhaust port 21b through which intake and exhaust (intake and exhaust) respectively flow, and valve guide fitting holes 21c and 21d opened to open to the intake port 21a and the exhaust port 21b, respectively. A combustion chamber ceiling surface 21e constituting the ceiling of the combustion chamber 30 is formed.

  In the intake port 21a, an intake opening 21g that is an intake inlet is formed on one side surface 21f of the cylinder head body 21, and an intake valve seat 33 that is an intake outlet is embedded in a portion that opens to the combustion chamber 30, and the intake opening 21g To the intake valve seat 33 while extending in a convex shape. An opening 33j on the combustion chamber 30 side of the intake valve seat 33 is an outlet of the intake port 21a.

In addition, the intake port 21a is integrally formed so that a partition wall 21h that vertically partitions the intake passage is substantially along the upper portion 21k and the lower portion 21m of the inner surface 21j of the intake port 21a, and the upper intake passage 35 is located above the partition wall 21h. A lower intake passage 36 is formed on the lower side.
An intake pipe 41 is connected to one side surface 21f of the cylinder head body 21 via a spacer 38 so as to communicate with the intake port 21a. To the upstream side of the intake pipe 41, components constituting an intake device such as a slot body, a connecting tube, and an air cleaner are connected.

The spacer 38 and the intake pipe 41 are also formed with partition walls 38a and 41a that divide the interior of the spacer 38 and the intake pipe 41 in the vertical direction. The upper intake passages 43 and 44 are provided above the partition walls 38a and 41a, and the lower intake passages 46 and 47 are provided below. Are formed respectively.
The upper intake passages 35, 43 and 44 described above constitute an upper passage 51, and the lower intake passages 36, 46 and 47 constitute a lower passage 52.

The throttle body connected to the upstream side of the intake pipe 41 is provided with an intake distribution valve that distributes intake air into an upper passage 51 and a lower passage 52. The intake distribution valve closes the inlet of the upper passage 51 and opens the inlet of the lower passage 52 in a low load state of the internal combustion engine 10, so that the intake air reaches the combustion chamber 30 through the lower passage 52. At this time, tumble can be generated in the combustion chamber 30 by the intake air flowing into the combustion chamber 30 from the lower intake passage 36 of the intake port 21a. The imaginary line shown in the combustion chamber 30 in the figure indicates a tumble flow.
In the middle and high load state of the internal combustion engine 10, both the upper passage 51 and the lower passage 52 are opened, so that the intake air passes through the upper passage 51 and the lower passage 52 to the combustion chamber 30.

In the exhaust port 21b, an exhaust opening 21p that is an exhaust inlet is formed on the other side surface 21n of the cylinder head body 21, and an exhaust valve seat 54 that is an exhaust outlet is embedded in a portion that opens to the combustion chamber 30, and the exhaust opening 21p To the exhaust valve seat 54 while extending in a convex shape. The opening 54j on the combustion chamber 30 side of the exhaust valve seat 54 is an outlet of the exhaust port 21b.
The valve guide fitting holes 21c and 21d are portions into which the cylindrical intake valve guide 56 and the exhaust valve guide 57 are respectively fitted.
The combustion chamber ceiling surface 21e is formed in a substantially dome-shaped surface with a high center, a plug mounting hole is opened in the combustion chamber ceiling surface 21e, and an ignition plug is mounted in the plug mounting hole.

The valve mechanism 22 includes a camshaft 60, an intake rocker shaft 61, an intake rocker arm 62, an intake valve 63, an intake valve spring 64, an exhaust rocker shaft 71, an exhaust rocker arm 72, an exhaust valve 73, and an exhaust valve spring 74.
The camshaft 60 is rotatably supported by the cylinder head body 21, and an intake cam 60a and an exhaust cam 60b are integrally formed.

  The intake rocker shaft 61 is disposed offset from one side of the camshaft 60 and supported by the cylinder head body 21. The intake rocker arm 62 is swingably supported by the intake rocker shaft 61, a roller 81 that rotates while hitting the intake cam 60a of the camshaft 60 is provided at one end, and an adjustment bolt 82 is screwed to the other end. ing. The adjustment bolt 82 is prevented from rotating by a lock nut 83.

  The intake valve 63 includes a shaft portion 63a that is slidably supported by the intake valve guide 56, and an umbrella portion 63b that is integrally provided at the lower end portion of the shaft portion 63a. The upper end of the shaft portion 63a is pressed against the adjustment bolt 82. The umbrella portion 63b is formed with an annular male taper-shaped valve seal surface, and this valve seal surface is in close contact with the annular female taper-shaped valve seat seal surface formed on the intake valve seat 33. The opening 33j serving as the outlet of 21a is closed.

  The intake valve spring 64 is disposed so as to be sandwiched between a lower retainer 85 placed on the pedestal 21q of the cylinder head body 21 and an upper retainer 86 attached to the tip of the shaft 63a of the intake valve 63. ing. Due to the elastic force of the intake valve spring 64, the umbrella portion 63 b of the intake valve 63 is pressed against and closely contacts the intake valve seat 33. In the figure, since the roller 81 of the intake rocker arm 62 rides on the peak portion of the intake cam 60a, the intake rocker arm 62 swings counterclockwise around the intake rocker shaft 61, and the intake rocker arm 62 is adjusted. The bolt 82 is in a state where the upper end of the shaft portion 63a of the intake valve 63 is pushed down. As a result, the umbrella portion 63b of the intake valve 63 is separated from the intake valve seat 33, and the intake port 21a is open.

  The exhaust rocker shaft 71 is offset from the upper side of the camshaft 60 to the other side and is supported by the cylinder head body 21. The exhaust rocker arm 72 is swingably supported by the exhaust rocker shaft 71, a roller 81 that rotates while hitting the exhaust cam 60b of the camshaft 60 is provided at one end, and an adjustment bolt 82 is screwed to the other end. ing. The adjustment bolt 82 is prevented from rotating by a lock nut 83.

  The exhaust valve 73 includes a shaft portion 73a that is slidably supported by the exhaust valve guide 57, and an umbrella portion 73b that is integrally provided at the lower end portion of the shaft portion 73a. The upper end of the shaft portion 73a is pressed against the adjustment bolt 82. The umbrella portion 73b is formed with an annular male taper-shaped valve seal surface, and this valve seal surface is in close contact with the annular female taper-shaped valve seat seal surface formed on the exhaust valve seat 54. The opening 54j serving as the outlet of 21b is closed.

  The exhaust valve spring 74 is disposed so as to be sandwiched between a lower retainer 85 placed on the pedestal 21r of the cylinder head body 21 and an upper retainer 86 attached to the tip of the shaft 73a of the exhaust valve 73. ing. Due to the elastic force of the exhaust valve spring 74, the umbrella portion 73 b of the exhaust valve 73 is pressed against and closely contacts the exhaust valve seat 54.

FIG. 2 is a cross-sectional view showing a state in which the intake valve 63 and the exhaust valve 73 are closed.
The intake valve seat 33 has a cylindrical shape, and an annular female taper-shaped seat seal surface 33c is formed at a corner between an inner peripheral surface 33a thereof and an end surface 33b facing the combustion chamber 30.
Further, the intake valve 63 is formed with a valve seal surface 63c that can be in close contact with the seat seal surface 33c of the intake valve seat 33 at the umbrella portion 63b. The valve seal surface 63c is an annular male tapered portion. In the figure, the seat seal surface 33c and the valve seal surface 63c are in close contact with each other and the intake port 21a is closed.

The exhaust valve seat 54 has a cylindrical shape. An annular female taper seat seal surface 54c and a cylindrical inner end periphery are formed at corners of the inner peripheral surface 54a and the end surface 54b facing the combustion chamber 30. A surface 54d is formed.
The inner peripheral surface 54d of the end portion is formed from the intake valve 63 with respect to the axis 54e of the exhaust valve seat 54 that is coaxial with the axis 73e of the exhaust valve 73 (that is, the axis 73e of the exhaust valve 73 and the axis 73e of the umbrella 73b). This is a portion having an axis 54f that is offset to the far side. That is, the end inner peripheral surface 54d is processed into a cylindrical shape on the exhaust valve seat 54 by a cutting tool such as an end mill, with the axis 54f as the center. The inner diameter of the end inner peripheral surface 54d is formed larger than the inner diameter of the inner peripheral surface 54a of the exhaust valve seat 54.

Further, the exhaust valve 73 includes a valve seal surface 73c that can be in close contact with the umbrella seal portion 73b and a seat seal surface 54c of the exhaust valve seat 54, and an outer peripheral surface 73f that has a cylindrical outer peripheral shape adjacent to the valve seal surface 73c. Is formed. The valve seal surface 73c is an annular and male tapered portion. In the figure, the seat seal surface 54c and the valve seal surface 73c are in close contact with each other and the exhaust port 21b is closed. The axis 73e of the exhaust valve 73 is also the axis of the outer peripheral surface 73f of the umbrella portion 73b.
The clearance between the end inner peripheral surface 54d of the exhaust valve seat 54 and the outer peripheral surface 73f of the umbrella portion 73b of the exhaust valve 73 is defined as CL. In the present embodiment, the clearance CL is made different in the circumferential direction of the exhaust valve 73 as described below.
A portion of the end inner peripheral surface 54d that is closest to the intake valve 63 is a nearby inner peripheral surface 54g, and a portion of the end inner peripheral surface 54d that is farthest from the intake valve 63 is a distant inner peripheral surface 54h. When the clearance CL between the near inner peripheral surface 54g and the outer peripheral surface 73f of the umbrella portion 73b is the near clearance CN, and the clearance CL between the far inner peripheral surface 54h and the outer peripheral surface 73f of the umbrella portion 73b is the far clearance CF, the near clearance CN The far clearance CF is large. The near inner peripheral surface 54g and the far inner peripheral surface 54h are located on a straight line 89 (see FIG. 5) described later.

FIG. 3 is a cross-sectional view showing the operation of the intake valve 63 and the exhaust valve 73.
In the intake stroke in which the intake valve 63 is opened and intake air is taken into the combustion chamber 30 through the intake port 21a from the intake device such as an air cleaner of the internal combustion engine 10 (see FIG. 1), the combustion chamber 30 enters the exhaust port 21b. When the exhaust valve 73 is opened due to valve overlap or when the exhaust valve 73 that is closed once is slightly opened, internal EGR is performed to return the exhaust gas once exhausted into the combustion chamber 30. This internal EGR is also called “EGR by opening twice” of the exhaust valve 73.
In this internal EGR, if the exhaust valve seat in contact with the exhaust valve 73 has a general cylindrical shape, the exhaust is substantially evenly distributed in the circumferential direction from the gap between the exhaust valve seat and the umbrella portion 74b of the exhaust valve 73. 30. Therefore, when the intake valve 63 is opened to generate intake air tumble in the combustion chamber 30, the flow of exhaust gas flowing into the combustion chamber 30 near the intake valve 63 interferes with the formation of the tumble.

Therefore, in the present embodiment, as shown in FIG. 2, the intake valve 63 has a clearance CL between the end inner peripheral surface 54 d of the exhaust valve seat 54 and the outer peripheral surface 73 f of the umbrella portion 73 b of the exhaust valve 73. The far clearance CF of the portion farthest from the intake valve 63 is made larger than the proximity clearance CN of the nearest portion.
Thus, as shown in FIG. 3, when the intake valve 63 is opened, as shown by the arrow A, when the intake air flows into the combustion chamber 30 and a tumble is generated, it is returned from the exhaust port 21b. Exhaust gas is less likely to flow to the intake valve 63 side of the combustion chamber 30 and more easily flows to the side of the combustion chamber 30 away from the intake valve 63 as indicated by arrow B. As a result, the occurrence of tumble due to the return in the direction indicated by the arrow B of the exhaust can be promoted without disturbing the occurrence of tumble.

FIG. 4 is an enlarged view of a main part of FIG. 3 and shows the exhaust valve seat 54 and the exhaust valve 73.
When the exhaust valve 73 is opened to the maximum due to the internal EGR, the clearance between the seat seal surface 54c of the exhaust valve seat 54 and the valve seal surface 73c of the exhaust valve 73 is defined as an EGR valve clearance CE (EGR clearance).
The EGR valve clearance CE is larger than the near clearance CN and smaller than the far clearance CF (CN <CE <CF).
Since the EGR valve clearance CE is the same in the circumferential direction of the exhaust valve seat 54 and the umbrella portion 73b of the exhaust valve 73, on the side closer to the intake valve 63 (see FIG. 3), the proximity clearance CN is set closer to the EGR valve clearance CE. The return amount of exhaust gas returning from the exhaust port 21b into the combustion chamber 30 is reduced.

  Further, on the side far from the intake valve 63, the far clearance CF is made larger or the same as the EGR valve clearance CE to ensure the return amount of the exhaust gas returning from the exhaust port 21b to the combustion chamber 30. When the far clearance CF is made larger than the EGR valve clearance CE, the end inner peripheral surface 54d is further away from the outer peripheral surface 73f of the umbrella portion 73b. For this reason, the flow of the exhaust gas flowing into the combustion chamber 30 can be directed toward the peripheral wall of the combustion chamber 30 (the inner peripheral surface of the cylinder hole 12b (see FIG. 1)), which is indicated by an imaginary arrow in FIG. As described above, it is possible to follow the flow of the tumble generated in the combustion chamber 30.

FIG. 5 is a view taken in the direction of arrow V in FIG. 3, and is a view of the combustion chamber ceiling surface 21 e side as viewed from the axial direction of the exhaust valve 73.
The inner peripheral surface 54d of the end portion of the exhaust valve seat 54 and the outer peripheral surface 73f of the umbrella portion 73b of the exhaust valve 73 are each circular, and the axis 54f of the exhaust valve seat 54 (specifically, the inner peripheral surface 54d of the end portion) and the exhaust The axis 73e of the valve 73 (specifically, the outer peripheral surface 73f of the umbrella portion 73b) is offset in the direction in which the intake valve 63 and the exhaust valve 73 are arranged. For this reason, the clearance CL between the end inner peripheral surface 54d and the outer peripheral surface 73f gradually increases from the side closer to the intake valve 63 toward the far side.
That is, the area of the gap between the end inner peripheral surface 54d and the outer peripheral surface 73f gradually increases from the side closer to the intake valve 63 toward the far side (the end inner peripheral surface 54d and the outer peripheral surface 73f in the figure). A plurality of dots are drawn in the gaps between them.)

Therefore, the exhaust between the end inner peripheral surface 54d and the outer peripheral surface 73f returns compared to the case where the clearance CL between the end inner peripheral surface 54d and the outer peripheral surface 73f is partially increased on the side far from the intake valve 63. The area of the passage can be increased, and the flow rate of the returning exhaust gas can be easily ensured. In addition, the code | symbol 21w in a figure is a plug attachment hole in which a spark plug is attached.
The direction in which the intake valve 63 and the exhaust valve 73 are aligned is a direction orthogonal to the camshaft 60 (see FIG. 1) and a direction orthogonal to the axis 54e of the exhaust valve seat 54 and the axis 73e of the exhaust valve 73. is there. For example, even if there are two intake valves 63, one exhaust valve 73, or a plurality of intake valves 63 and exhaust valves 73, the direction in which the intake valves 63 and the exhaust valves 73 are arranged is the same as described above.
Reference numeral 89 is a straight line that passes through the axis line 54e of the exhaust valve seat 54 and the axis line 73e of the exhaust valve 73 and is orthogonal to the camshaft 60. The axis line 54f is located on the straight line 89. Further, the inner peripheral surface 54 g and the far inner peripheral surface 54 h indicated by black circles are also located on the straight line 89.

As shown in FIGS. 1 and 2, the cylinder head 14 is formed with the combustion chamber 30 and intake / exhaust ports 21a and 21b communicating with the combustion chamber 30, and the intake and exhaust ports 21a and 21b are opened to the combustion chamber 30. 33j and 54j are opened and closed by intake and exhaust valves 63 and 73, and a partition wall 21h for generating tumble of intake air in the combustion chamber 30 is provided in the intake port 21a, and the intake air flowing through the intake port 21a by the partition wall 21h. Is divided into an upper intake passage 35 and a lower intake passage 36 as upper and lower intake passages that are divided into upper and lower portions, and the exhaust valve 73 is opened and the internal EGR is performed while the intake valve 63 is open. As an outer peripheral edge of the inner peripheral surface 54d of the end portion formed in the opening 54j on the combustion chamber 30 side of the exhaust port 21b and the umbrella portion 73b of the exhaust valve 73 Clearance CL between the outer peripheral surface 73f is different in the circumferential direction of the umbrella portions 73b of the exhaust valve 73.
According to this configuration, while suppressing the pressure loss in the exhaust port 21b, the flow of exhaust gas flowing into the combustion chamber 30 in the direction of prompting the tumble of intake air can be formed in the internal EGR by the exhaust valve 73. It becomes possible, and combustion efficiency can be improved.

  Further, when the clearance CL closer to the intake valve 63 is the near clearance CN and the clearance CL far from the intake valve 63 is the far clearance CF, the far clearance CF is larger than the near clearance CN. By changing the clearance between the end inner peripheral surface 54d of the opening 54j on the combustion chamber 30 side of the port 21b and the outer peripheral surface 73f of the umbrella portion 73b of the exhaust valve 73 between the side closer to the intake valve 63 and the side far from the intake valve 63. During internal EGR, the flow of exhaust gas flowing into the combustion chamber 30 so as to promote the tumble of the intake air can be formed, and the combustion efficiency can be improved.

  Further, as shown in FIG. 5, the clearance CL gradually decreases from the exhaust valve 73 side toward the intake valve 63 side. Therefore, the end inner peripheral surface 54 d of the opening 54 j on the combustion chamber 30 side and the exhaust valve 73. The area between the outer peripheral surface 73f of the umbrella portion 73b increases on the side far from the intake valve 63, and exhaust can be effectively taken into the combustion chamber 30 to promote tumble, thereby further improving the combustion efficiency. be able to.

  Further, as shown in FIG. 4, an exhaust valve seat 54 as a valve seat that closes the exhaust port 21b by contacting the umbrella portion 73b of the exhaust valve 73 is provided at the opening 54j on the combustion chamber 30 side of the exhaust port 21b. The maximum clearance between the valve seal surface 73c as the sealing surface of the umbrella portion 73b of the exhaust valve 73 and the seat seal surface 54c as the seal surface of the exhaust valve seat 54 that is opened while the intake valve 63 is open is defined as EGR. When the valve clearance (EGR clearance) CE is set, the EGR valve clearance CE is larger than the proximity clearance CN, and the far clearance CF is larger than the EGR valve clearance CE. Therefore, the far clearance CF should be larger than the EGR valve clearance CE. With the specified EGR valve clear Opening the exhaust valve 73 so that Nsu, can be made to flow along the tumble flow in the combustion chamber 30 through the gap which becomes the discharge and distant clearance CF from the exhaust port 21b. Further, by making the proximity clearance CN smaller than the EGR valve clearance CE, it is possible to make it difficult for the exhaust to flow into the intake valve 63 side of the combustion chamber 30 so as not to disturb the tumble flow.

  2 and 5, the end inner peripheral surface 54d is formed on the exhaust valve seat 54 as a valve seat, and the clearance CL is defined by the axis 54f of the end inner peripheral surface 54d and the exhaust valve 73. Since it is made to differ in the circumferential direction of the umbrella part 73b by offsetting in the direction (specifically, the direction away from the intake valve 63) where the intake and exhaust valves 63 and 73 are arranged with respect to the axis 73e, the exhaust valve seat 54 The clearance CL can be easily varied in the circumferential direction of the umbrella portion 73b simply by processing the simple circular end inner peripheral surface 54d, thereby reducing the cost and productivity of the internal combustion engine 10 (see FIG. 1). Improvements can be made.

The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified and applied without departing from the gist of the present invention.
The internal combustion engine 10 of the present invention can be applied to, for example, a motorcycle, a saddle-type vehicle other than a motorcycle, an internal combustion engine mounted on an automobile, and an internal combustion engine mounted on an industrial machine other than the vehicle.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Cylinder head 21a Intake port 21b Exhaust port 21h Partition wall 30 Combustion chamber 33j Opening 35 Upper intake passage (intake passage)
36 Lower intake passage (intake passage)
54 Exhaust valve seat (valve seat)
54c Seat seal surface (seal surface)
54d End inner peripheral surface 54f End inner peripheral surface 54j Opening 63 Intake valve 73 Exhaust valve 73b Umbrella 73c Valve seal surface (seal surface)
73e Exhaust valve axis 73f Outer peripheral surface (outer peripheral edge)
CE EGR valve clearance (EGR clearance)
CF Distance clearance CL clearance CN Near clearance

Claims (4)

The cylinder head (14) is formed with a combustion chamber (30) and intake / exhaust ports (21a, 21b) communicating with the combustion chamber (30), and the intake / exhaust ports (21a, 21b) are connected to the combustion chamber (30). Openings (33j, 54j) are opened and closed by intake and exhaust valves (63, 73), and a partition plate (21h) for generating tumble of intake air in the combustion chamber (30) is provided at the intake port (21a). The partition plate (21h) divides the intake air flowing through the intake port (21a) into upper and lower intake passages (35, 36) that are vertically divided, and the intake valve (63) is open. In the internal combustion engine in which the exhaust valve (73) is opened and internal EGR is performed,
A valve seat (54) that closes the exhaust port (21b) by hitting the umbrella portion (73b) of the exhaust valve (73) against the opening (54j) of the exhaust port (21b) on the combustion chamber (30) side. Provided,
The clearance (CL) between the cylindrical inner peripheral surface (54d) formed on the valve seat (54) and the outer peripheral edge (73f) of the umbrella part (73b) of the exhaust valve (73) is the umbrella. Unlike in the circumferential direction of the parts (73b),
When the clearance (CL) on the side close to the intake valve (63) is the proximity clearance (CN) and the clearance (CL) on the side far from the intake valve (63) is the far clearance (CF), the vicinity internal combustion agencies clearance (CN) said distal clearance than (CF) is characterized that you have been large. The internal combustion engine according to claim 1, wherein the clearance (CL) gradually decreases from the exhaust valve (73) side toward the intake valve (63) side. The maximum of the sealing surface (73c) of the umbrella portion (73b) of the exhaust valve (73) and the sealing surface (54c) of the valve seat (54) opened while the intake valve (63) is open. When the clearance is EGR clearance (CE), the EGR clearance (CE) is larger than the near clearance (CN), and the far clearance (CF) is larger than the EGR clearance (CE). The internal combustion engine according to claim 2 . The clearance (CL) offsets the axis (54f) of the inner peripheral surface (54d) of the end in the direction in which the intake / exhaust valves (63, 73) are aligned with the axis (73e) of the exhaust valve (73). The internal combustion engine according to claim 3 , wherein the internal combustion engine is made different in the circumferential direction of the umbrella portion (73b).

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